<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>

</body>
<script>

    var a = 1;

    console.log(Object.getOwnPropertyDescriptor(window,"a"))

    delete window.a
    console.log(window.a)


</script>
</html>